1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to new and improved zoned demand elevator supervisory systems.
2. Description of the Prior Art
Zoned demand elevator systems, such as the elevator system disclosed in U.S. Pat. No. 3,256,958, which is assigned to the same assignee as the present application, provide highly efficient elevator service by attempting to serve a new hall call with a suitably conditioned busy elevator car and if the hall call cannot be so allocated to a busy car, a demand is registered for an available car. When a busy elevator car completes its assigned tasks, and has no car calls or hall calls ahead of its travel direction, it becomes available for assignment at the floor of its last stop. When a demand for an available car is registered, the closest available car to the floor of the building which initiated the demand is given the assignment.
The zoned demand elevator system of the hereinbefore mentioned U.S. Pat. No. 3,256,958 is especially well suited for large banks of high speed elevator cars in high rise buildings, and the system is extremely flexible in order to accommodate the wide variations in traffic demands associated with such a structure.
In order to extend the zoned demand concept to smaller banks of elevator cars in a low rise building, or in a building with moderate traffic demands, where cost considerations do not justify the sophistication of the system provided by the aforesaid U.S. patent, the system disclosed in U.S. Pat. No. 3,504,771 was developed, which patent is also assigned to the same assignee as the present application. The system disclosed in U.S. Pat. No. 3,504,771 is most advantageous for banks of cars up to and including three elevator cars. The building is divided by the supervisory control into two zones of floors in addition to a main floor and basement. When a car becomes available, it is identified as being available for a specific zone, which may or may not be the zone in which it is physically located, and the zone for which the car is available can be changed as circumstances change.
The zoned demand system of U.S. Pat. No. 3,504,771 has been very successful in providing efficient elevator service for low rise buildings, and does so at a lower cost than would be incurred by using the more sophisticated, more flexible zoned demand supervisory systems developed primarily for high rise, high speed elevator banks.
There are many low rise buildings which require a bank of four or five elevator cars, and the supervisory systems for such as installation do not require the flexibility essential in elevator systems for high rise buildings. Thus it would be desirable to provide a new and improved zoned demand supervisory elevator system capable of efficiently handling four or five cars in a building having up to a maximum of about forty floors, which system should be less costly than the highly flexible high rise supervisory systems, but it should provide excellent service for low rise buildings.